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Last week I was looking at the top viewed posts on my blog and I noticed that visitors are interested in the authentication part of ASP.NET Web API, CORS Support, and how to authenticate users in single page applications built with AngularJS using token based approach.

So I decided to compile mini tutorial of three five posts which covers and connects those topics. In this tutorial we’ll build SPA using AngularJS for the front-end, and ASP.NET Web API 2, Owin middleware, and ASP.NET Identity for the back-end.

Token Based Authentication

As I stated before we’ll use token based approach to implement authentication between the front-end application and the back-end API, as we all know the common and old way to implement authentication is the cookie-based approach were the cookie is sent with each request from the client to the server, and on the server it is used to identify the authenticated user.

With the evolution of front-end frameworks and the huge change on how we build web applications nowadays the preferred approach to authenticate users is to use signed token as this token sent to the server with each request, some of the benefits for using this approach are:

Scalability of Servers: The token sent to the server is self contained which holds all the user information needed for authentication, so adding more servers to your web farm is an easy task, there is no dependent on shared session stores.

Loosely Coupling: Your front-end application is not coupled with specific authentication mechanism, the token is generated from the server and your API is built in a way to understand this token and do the authentication.

Mobile Friendly: Cookies and browsers like each other, but storing cookies on native platforms (Android, iOS, Windows Phone) is not a trivial task, having standard way to authenticate users will simplify our life if we decided to consume the back-end API from native applications.

What we’ll build in this tutorial?

The front-end SPA will be built using HTML5, AngularJS, and Twitter Bootstrap. The back-end server will be built using ASP.NET Web API 2 on top of Owin middleware not directly on top of ASP.NET; the reason for doing so that we’ll configure the server to issue OAuth bearer token authentication using Owin middleware too, so setting up everything on the same pipeline is better approach. In addition to this we’ll use ASP.NET Identity system which is built on top of Owin middleware and we’ll use it to register new users and validate their credentials before generating the tokens.

As I mentioned before our back-end API should accept request coming from any origin, not only our front-end, so we’ll be enabling CORS (Cross Origin Resource Sharing) in Web API as well for the OAuth bearer token provider.

Use cases which will be covered in this application:

Allow users to signup (register) by providing username and password then store credentials in secure medium.

Building the Back-End API

Step 1: Creating the Web API Project

In this tutorial I’m using Visual Studio 2013 and .Net framework 4.5, you can follow along using Visual Studio 2012 but you need to install Web Tools 2013.1 for VS 2012 by visiting this link.

Now create an empty solution and name it “AngularJSAuthentication” then add new ASP.NET Web application named “AngularJSAuthentication.API”, the selected template for project will be as the image below. Notice that the authentication is set to “No Authentication” taking into consideration that we’ll add this manually.

Step 2: Installing the needed NuGet Packages:

Now we need to install the NuGet packages which are needed to setup our Owin server and configure ASP.NET Web API to be hosted within an Owin server, so open NuGet Package Manger Console and type the below:

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Install-PackageMicrosoft.AspNet.WebApi.Owin -Version5.1.2

Install-PackageMicrosoft.Owin.Host.SystemWeb -Version2.1.0

The package “Microsoft.Owin.Host.SystemWeb” is used to enable our Owin server to run our API on IIS using ASP.NET request pipeline as eventually we’ll host this API on Microsoft Azure Websites which uses IIS.

Step 3: Add Owin “Startup” Class

Right click on your project then add new class named “Startup”. We’ll visit this class many times and modify it, for now it will contain the code below:

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usingMicrosoft.Owin;

usingOwin;

usingSystem;

usingSystem.Collections.Generic;

usingSystem.Linq;

usingSystem.Web;

usingSystem.Web.Http;

[assembly:OwinStartup(typeof(AngularJSAuthentication.API.Startup))]

namespaceAngularJSAuthentication.API

{

publicclassStartup

{

publicvoidConfiguration(IAppBuilder app)

{

HttpConfiguration config=newHttpConfiguration();

WebApiConfig.Register(config);

app.UseWebApi(config);

}

}

}

What we’ve implemented above is simple, this class will be fired once our server starts, notice the “assembly” attribute which states which class to fire on start-up. The “Configuration” method accepts parameter of type “IAppBuilder” this parameter will be supplied by the host at run-time. This “app” parameter is an interface which will be used to compose the application for our Owin server.

The “HttpConfiguration” object is used to configure API routes, so we’ll pass this object to method “Register” in “WebApiConfig” class.

Lastly, we’ll pass the “config” object to the extension method “UseWebApi” which will be responsible to wire up ASP.NET Web API to our Owin server pipeline.

Usually the class “WebApiConfig” exists with the templates we’ve selected, if it doesn’t exist then add it under the folder “App_Start”. Below is the code inside it:

Step 4: Delete Global.asax Class

No need to use this class and fire up the Application_Start event after we’ve configured our “Startup” class so feel free to delete it.

Step 5: Add the ASP.NET Identity System

After we’ve configured the Web API, it is time to add the needed NuGet packages to add support for registering and validating user credentials, so open package manager console and add the below NuGet packages:

The first package will add support for ASP.NET Identity Owin, and the second package will add support for using ASP.NET Identity with Entity Framework so we can save users to SQL Server database.

Now we need to add Database context class which will be responsible to communicate with our database, so add new class and name it “AuthContext” then paste the code snippet below:

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publicclassAuthContext:IdentityDbContext<IdentityUser>

{

publicAuthContext()

:base("AuthContext")

{

}

}

As you can see this class inherits from “IdentityDbContext” class, you can think about this class as special version of the traditional “DbContext” Class, it will provide all of the Entity Framework code-first mapping and DbSet properties needed to manage the identity tables in SQL Server. You can read more about this class on Scott Allen Blog.

Now we want to add “UserModel” which contains the properties needed to be sent once we register a user, this model is POCO class with some data annotations attributes used for the sake of validating the registration payload request. So under “Models” folder add new class named “UserModel” and paste the code below:

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publicclassUserModel

{

[Required]

[Display(Name="User name")]

publicstringUserName{get;set;}

[Required]

[StringLength(100,ErrorMessage="The {0} must be at least {2} characters long.",MinimumLength=6)]

[DataType(DataType.Password)]

[Display(Name="Password")]

publicstringPassword{get;set;}

[DataType(DataType.Password)]

[Display(Name="Confirm password")]

[Compare("Password",ErrorMessage="The password and confirmation password do not match.")]

publicstringConfirmPassword{get;set;}

}

Now we need to add new connection string named “AuthContext” in our Web.Config class, so open you web.config and add the below section:

What we’ve implemented above is the following: we are depending on the “UserManager” that provides the domain logic for working with user information. The “UserManager” knows when to hash a password, how and when to validate a user, and how to manage claims. You can read more about ASP.NET Identity System.

Step 7: Add our “Account” Controller

Now it is the time to add our first Web API controller which will be used to register new users, so under file “Controllers” add Empty Web API 2 Controller named “AccountController” and paste the code below:

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[RoutePrefix("api/Account")]

publicclassAccountController:ApiController

{

privateAuthRepository _repo=null;

publicAccountController()

{

_repo=newAuthRepository();

}

// POST api/Account/Register

[AllowAnonymous]

[Route("Register")]

publicasyncTask<IHttpActionResult>Register(UserModel userModel)

{

if(!ModelState.IsValid)

{

returnBadRequest(ModelState);

}

IdentityResult result=await_repo.RegisterUser(userModel);

IHttpActionResult errorResult=GetErrorResult(result);

if(errorResult!=null)

{

returnerrorResult;

}

returnOk();

}

protectedoverridevoidDispose(booldisposing)

{

if(disposing)

{

_repo.Dispose();

}

base.Dispose(disposing);

}

privateIHttpActionResult GetErrorResult(IdentityResult result)

{

if(result==null)

{

returnInternalServerError();

}

if(!result.Succeeded)

{

if(result.Errors!=null)

{

foreach(stringerror inresult.Errors)

{

ModelState.AddModelError("",error);

}

}

if(ModelState.IsValid)

{

// No ModelState errors are available to send, so just return an empty BadRequest.

returnBadRequest();

}

returnBadRequest(ModelState);

}

returnnull;

}

}

By looking at the “Register” method you will notice that we’ve configured the endpoint for this method to be “/api/account/register” so any user wants to register into our system must issue HTTP POST request to this URI and the pay load for this request will contain the JSON object as below:

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{

"userName":"Taiseer",

"password":"SuperPass",

"confirmPassword":"SuperPass"

}

Now you can run your application and issue HTTP POST request to your local URI: “http://localhost:port/api/account/register” or you can try the published API using this end point: http://ngauthenticationapi.azurewebsites.net/api/account/register if all went fine you will receive HTTP status code 200 and the database specified in connection string will be created automatically and the user will be inserted into table “dbo.AspNetUsers”.

Note: It is very important to send this POST request over HTTPS so the sensitive information get encrypted between the client and the server.

The “GetErrorResult” method is just a helper method which is used to validate the “UserModel” and return the correct HTTP status code if the input data is invalid.

Step 8: Add Secured Orders Controller

Now we want to add another controller to serve our Orders, we’ll assume that this controller will return orders only for Authenticated users, to keep things simple we’ll return static data. So add new controller named “OrdersController” under “Controllers” folder and paste the code below:

Notice how we added the “Authorize” attribute on the method “Get” so if you tried to issue HTTP GET request to the end point “http://localhost:port/api/orders” you will receive HTTP status code 401 unauthorized because the request you send till this moment doesn’t contain valid authorization header. You can check this using this end point: http://ngauthenticationapi.azurewebsites.net/api/orders

Step 9: Add support for OAuth Bearer Tokens Generation

Till this moment we didn’t configure our API to use OAuth authentication workflow, to do so open package manager console and install the following NuGet package:

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Install-PackageMicrosoft.Owin.Security.OAuth -Version2.1.0

After you install this package open file “Startup” again and call the new method named “ConfigureOAuth” as the first line inside the method “Configuration”, the implemntation for this method as below:

Here we’ve created new instance from class “OAuthAuthorizationServerOptions” and set its option as the below:

The path for generating tokens will be as :”http://localhost:port/token”. We’ll see how we will issue HTTP POST request to generate token in the next steps.

We’ve specified the expiry for token to be 24 hours, so if the user tried to use the same token for authentication after 24 hours from the issue time, his request will be rejected and HTTP status code 401 is returned.

We’ve specified the implementation on how to validate the credentials for users asking for tokens in custom class named “SimpleAuthorizationServerProvider”.

Now we passed this options to the extension method “UseOAuthAuthorizationServer” so we’ll add the authentication middleware to the pipeline.

Step 10: Implement the “SimpleAuthorizationServerProvider” class

Add new folder named “Providers” then add new class named “SimpleAuthorizationServerProvider”, paste the code snippet below:

context.SetError("invalid_grant","The user name or password is incorrect.");

return;

}

}

varidentity=newClaimsIdentity(context.Options.AuthenticationType);

identity.AddClaim(newClaim("sub",context.UserName));

identity.AddClaim(newClaim("role","user"));

context.Validated(identity);

}

}

As you notice this class inherits from class “OAuthAuthorizationServerProvider”, we’ve overridden two methods “ValidateClientAuthentication” and “GrantResourceOwnerCredentials”. The first method is responsible for validating the “Client”, in our case we have only one client so we’ll always return that its validated successfully.

The second method “GrantResourceOwnerCredentials” is responsible to validate the username and password sent to the authorization server’s token endpoint, so we’ll use the “AuthRepository” class we created earlier and call the method “FindUser” to check if the username and password are valid.

If the credentials are valid we’ll create “ClaimsIdentity” class and pass the authentication type to it, in our case “bearer token”, then we’ll add two claims (“sub”,”role”) and those will be included in the signed token. You can add different claims here but the token size will increase for sure.

Now generating the token happens behind the scenes when we call “context.Validated(identity)”.

To allow CORS on the token middleware provider we need to add the header “Access-Control-Allow-Origin” to Owin context, if you forget this, generating the token will fail when you try to call it from your browser. Not that this allows CORS for token middleware provider not for ASP.NET Web API which we’ll add on the next step.

Step 11: Allow CORS for ASP.NET Web API

First of all we need to install the following NuGet package manger, so open package manager console and type:

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Install-PackageMicrosoft.Owin.Cors -Version2.1.0

Now open class “Startup” again and add the highlighted line of code (line 8) to the method “Configuration” as the below:

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publicvoidConfiguration(IAppBuilder app)

{

HttpConfiguration config=newHttpConfiguration();

ConfigureOAuth(app);

WebApiConfig.Register(config);

app.UseCors(Microsoft.Owin.Cors.CorsOptions.AllowAll);

app.UseWebApi(config);

}

Step 12: Testing the Back-end API

Assuming that you registered the username “Taiseer” with password “SuperPass” in the step below, we’ll use the same username to generate token, so to test this out open your favorite REST client application in order to issue HTTP requests to generate token for user “Taiseer”. For me I’ll be using PostMan.

Notice that the content-type and payload type is “x-www-form-urlencoded” so the payload body will be on form (grant_type=password&username=”Taiseer”&password=”SuperPass”). If all is correct you’ll notice that we’ve received signed token on the response.

As well the “grant_type” Indicates the type of grant being presented in exchange for an access token, in our case it is password.

Now we want to use this token to request the secure data using the end point http://ngauthenticationapi.azurewebsites.net/api/orders so we’ll issue GET request to the end point and will pass the bearer token in the Authorization header, so for any secure end point we’ve to pass this bearer token along with each request to authenticate the user.

Note: that we are not transferring the username/password as the case of Basic authentication.

The GET request will be as the image below:

If all is correct we’ll receive HTTP status 200 along with the secured data in the response body, if you try to change any character with signed token you directly receive HTTP status code 401 unauthorized.

Now our back-end API is ready to be consumed from any front end application or native mobile app.

Update (2014-08-11) Thanks for Attila Hajdrik for forking my repo and updating it to use MongoDb instead of Entity Framework, you can check it here.

hi, after the Web Api is deployed on Azure, token does not work anymore. Every request towards the webApi (with this token in the header of http request ) tells the 401 unauthorized status..please help what am i missing

Thanks for your post.
I have to questions :
1- how to implement a refresh token as a continue of this work in both of (API and Client)?
2- when user is logged in then his roles are changed by the admin, his is still can access the some methods even in the database [AspNetUserRoles] he doesn’t has this rights.

Hello Fawzy,
1: Please check this post which should help you in implementing refresh tokens.
2: The access token is self-contained, so it will have the old roles (claims) until the user log in again and grabs the new claims from the DB, if you implemented refresh tokens then you can set the access token to expire in a short period (i.e 1 hour) so the effect of this is reduced.

Hello Taiseer,
Thanks for your reply, i followed the steps of your post then i did it finally.
In the refresh token method in the Auth. Server i made a refresh [Reloading] for the roles in the access token directly from the DB, and it worked fine.

In my project, i have Implemented web api with token based authentication.

And accessing this api from angular js,

Basically, I need 20 min session time out for web api in case user is not performing any action since last 20 min. To achieve this, I have setup 20 min time out for token expiration as below. But problem is, even though I am doing actions in site and requesting web api though after 20 min, token gets expires.